1. Field of the Invention
The present invention relates to detecting vibration within a hard disk drive.
2. Background Information
Hard disk drives contain a plurality of magnetic heads that are coupled to rotating disks. The heads write and read information by magnetizing and sensing the magnetic fields of the disk surfaces. Each head is attached to a flexure arm to create a subassembly commonly referred to as a head gimbal assembly (“HGA”). The HGA's are suspended from an actuator arm. The actuator arm has a voice coil motor that can move the heads across the surfaces of the disks.
Information is typically stored in radial tracks that extend across the surface of each disk. Each track is typically divided into a number of segments or sectors. The voice coil motor and actuator arm can move the heads to different tracks of the disks.
Disk drives typically employ a servo to maintain the heads on the centers of the tracks. Deviations from the track center line may create errors in the reading and/or writing of data. The drive may be subjected to vibration. For example, disk drives have a spindle motor that rotates the disks relative to the heads. Rotation of the spindle motor may create a vibration that is transmitted through the drive.
Some disk drives contain an accelerometer that detects the presence of vibration. The output of the accelerometer is fed to the servo system which then compensates for the vibration. The inclusion of an accelerometer increases the cost and complexity of mass producing disk drives. It would be desirable to detect vibration without an accelerometer.